(i) Field of the Invention
The present invention relates to a body motion measuring apparatus which can be worn or carried freely and can measure a predetermined body motion (e.g., walking).
(ii) Description of the Related Art
In recent years, a pedometer is provided that can always detect a vibrational component in a vertical direction even if the direction of the device held is changed when a user who carries it in a pocket or a bag or on a waist belt changes his position.
Heretofore, such a pedometer has such techniques as disclosed in Patent Publications 1 and 2.
To brief the techniques, a pedometer in Patent Publication 1 comprises a plurality of acceleration sensors differing from one another in detection directions and an angle detection sensor in a main unit, detects the direction (angle) of the main unit by the angle detection sensor, selects an acceleration sensor capable of detection at the direction (angle) of the main unit from the plurality of acceleration sensors, and counts steps based on a detection signal from the selected acceleration sensor.
Meanwhile, a body motion detection device in Patent Publication 2 comprises a plurality of acceleration sensors (body motion sensors) differing from each other in detection directions in a main unit, performs the waveform processings of the acceleration sensors, selects one of the acceleration sensors if the number of acceleration waveforms obtained from output signals of the one of the acceleration sensors stored in a buffer 1 is equal to or larger than the number of acceleration waveforms obtained from output signals of the one of the acceleration sensors stored in a buffer 2 after passage of a predetermined time period or, if not, selects the other acceleration sensor, and counts steps based on a detection signal from the selected acceleration sensor.
Patent Publication 1
Japanese Patent Laid-Open Publication No. 9-223214
Patent Publication 2
Japanese Patent Laid-Open Publication No. 2002-191580
However, the above pedometer in Patent Publication 1 has a problem that use of the angle detection sensor causes high costs. Meanwhile, the above body motion detection device in Patent Publication 2 has a problem that when the direction of the body motion detection device held changes, a detection output from the acceleration sensor changes according to the angle at which the device has been inclined as exemplified by the relationship between angles and detection outputs as represented by the graph shown in FIG. 15, so that the detection output is not determined to be a value to be counted as a step by subsequent steps, resulting in an error in the number of counted steps.
Thus, an object of the present invention is to solve the above problems of the prior art and provide a body motion measuring apparatus which measures a predetermined body motion at low costs and with reduced errors.